Gerromorpha (Hemiptera: Heteroptera) comprises more than 2100 species of semiaquatic bugs, most of which have the ability to walk on the surface of the water. So far, 238 species have been recorded from Brazil, but several portions of the country remain poorly explored. The Metropolitan Region of Santarém (MRS), Pará State, Brazil, lacks faunistic and taxonomic studies concerning this group and the local fauna is under threat due to human actions.
Aiming to fill gaps concerning the diversity and distribution of Gerromorpha in the Amazon, a survey of the semi-aquatic bugs from the MRS is presented. Collections were made in 33 aquatic ecosystems in the different phytophysiognomies within this area from July 2019 to October 2020. As a result, a checklist with 44 species recorded from the three municipalities of the MRS is presented. Furthermore, three new species of the genus Microvelia Westwood, 1834 (M. belterrensis sp. nov., M. hamadae sp. nov. and M. sousorum sp. nov.) are described, two species are recorded for the first time from Brazil (Microvelia aschnakiranae Makhan, 2014 and Rhagovelia graziae Galindo-Malagón, Morales & Moreira, 2021), two from Pará State (Microvelia longipes Uhler, 1894 and Paravelia dilatata Polhemus & Polhemus, 1984) and 15 from the MRS (Brachymetra lata Shaw, 1933, B. shawi Hungerford & Matsuda, 1957, Tachygerris adamsoni (Drake, 1942), Microvelia pulchella Westwood, 1834, Rhagovelia brunae Magalhães & Moreira, 2016, R. evidis Bacon, 1948, R. jubata Bacon, 1948, Callivelia conata (Hungerford, 1929), Oiovelia cunucunumana Drake & Maldonado-Capriles, 1952, Paravelia bullialata Polhemus & Polhemus, 1984, Stridulivelia alia (Drake, 1957), S. stridulata (Hungerford, 1929), S. strigosa (Hungerford, 1929), S. tersa (Drake & Harris, 1941) and S. transversa (Hungerford, 1929)).
